Merging upstream version 1.46.3.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 0 insertions, 1361 deletions

diff --git a/database/engine/rrdengineapi.c b/database/engine/rrdengineapi.c
deleted file mode 100755
index 1ddce5243..000000000
--- a/database/engine/rrdengineapi.c
+++ /dev/null
@@ -1,1361 +0,0 @@
-// SPDX-License-Identifier: GPL-3.0-or-later
-
-#include "database/engine/rrddiskprotocol.h"
-#include "rrdengine.h"
-
-/* Default global database instance */
-struct rrdengine_instance multidb_ctx_storage_tier0;
-struct rrdengine_instance multidb_ctx_storage_tier1;
-struct rrdengine_instance multidb_ctx_storage_tier2;
-struct rrdengine_instance multidb_ctx_storage_tier3;
-struct rrdengine_instance multidb_ctx_storage_tier4;
-
-#define mrg_metric_ctx(metric) (struct rrdengine_instance *)mrg_metric_section(main_mrg, metric)
-
-#if RRD_STORAGE_TIERS != 5
-#error RRD_STORAGE_TIERS is not 5 - you need to add allocations here
-#endif
-struct rrdengine_instance *multidb_ctx[RRD_STORAGE_TIERS];
-uint8_t tier_page_type[RRD_STORAGE_TIERS] = {PAGE_METRICS, PAGE_TIER, PAGE_TIER, PAGE_TIER, PAGE_TIER};
-
-#if defined(ENV32BIT)
-size_t tier_page_size[RRD_STORAGE_TIERS] = {2048, 1024, 192, 192, 192};
-#else
-size_t tier_page_size[RRD_STORAGE_TIERS] = {4096, 2048, 384, 384, 384};
-#endif
-
-#if PAGE_TYPE_MAX != 2
-#error PAGE_TYPE_MAX is not 2 - you need to add allocations here
-#endif
-
-size_t page_type_size[256] = {
-        [PAGE_METRICS] = sizeof(storage_number),
-        [PAGE_TIER] = sizeof(storage_number_tier1_t),
-        [PAGE_GORILLA_METRICS] = sizeof(storage_number)
-};
-
-__attribute__((constructor)) void initialize_multidb_ctx(void) {
-    multidb_ctx[0] = &multidb_ctx_storage_tier0;
-    multidb_ctx[1] = &multidb_ctx_storage_tier1;
-    multidb_ctx[2] = &multidb_ctx_storage_tier2;
-    multidb_ctx[3] = &multidb_ctx_storage_tier3;
-    multidb_ctx[4] = &multidb_ctx_storage_tier4;
-}
-
-int db_engine_journal_check = 0;
-int default_rrdeng_disk_quota_mb = 256;
-int default_multidb_disk_quota_mb = 256;
-
-#if defined(ENV32BIT)
-int default_rrdeng_page_cache_mb = 16;
-int default_rrdeng_extent_cache_mb = 0;
-#else
-int default_rrdeng_page_cache_mb = 32;
-int default_rrdeng_extent_cache_mb = 0;
-#endif
-
-// ----------------------------------------------------------------------------
-// metrics groups
-
-static inline void rrdeng_page_alignment_acquire(struct pg_alignment *pa) {
-    if(unlikely(!pa)) return;
-    __atomic_add_fetch(&pa->refcount, 1, __ATOMIC_SEQ_CST);
-}
-
-static inline bool rrdeng_page_alignment_release(struct pg_alignment *pa) {
-    if(unlikely(!pa)) return true;
-
-    if(__atomic_sub_fetch(&pa->refcount, 1, __ATOMIC_SEQ_CST) == 0) {
-        freez(pa);
-        return true;
-    }
-
-    return false;
-}
-
-// charts call this
-STORAGE_METRICS_GROUP *rrdeng_metrics_group_get(STORAGE_INSTANCE *db_instance __maybe_unused, uuid_t *uuid __maybe_unused) {
-    struct pg_alignment *pa = callocz(1, sizeof(struct pg_alignment));
-    rrdeng_page_alignment_acquire(pa);
-    return (STORAGE_METRICS_GROUP *)pa;
-}
-
-// charts call this
-void rrdeng_metrics_group_release(STORAGE_INSTANCE *db_instance __maybe_unused, STORAGE_METRICS_GROUP *smg) {
-    if(unlikely(!smg)) return;
-
-    struct pg_alignment *pa = (struct pg_alignment *)smg;
-    rrdeng_page_alignment_release(pa);
-}
-
-// ----------------------------------------------------------------------------
-// metric handle for legacy dbs
-
-/* This UUID is not unique across hosts */
-void rrdeng_generate_legacy_uuid(const char *dim_id, const char *chart_id, uuid_t *ret_uuid)
-{
-    EVP_MD_CTX *evpctx;
-    unsigned char hash_value[EVP_MAX_MD_SIZE];
-    unsigned int hash_len;
-
-    evpctx = EVP_MD_CTX_create();
-    EVP_DigestInit_ex(evpctx, EVP_sha256(), NULL);
-    EVP_DigestUpdate(evpctx, dim_id, strlen(dim_id));
-    EVP_DigestUpdate(evpctx, chart_id, strlen(chart_id));
-    EVP_DigestFinal_ex(evpctx, hash_value, &hash_len);
-    EVP_MD_CTX_destroy(evpctx);
-    fatal_assert(hash_len > sizeof(uuid_t));
-    memcpy(ret_uuid, hash_value, sizeof(uuid_t));
-}
-
-static METRIC *rrdeng_metric_get_legacy(STORAGE_INSTANCE *db_instance, const char *rd_id, const char *st_id) {
-    struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
-    uuid_t legacy_uuid;
-    rrdeng_generate_legacy_uuid(rd_id, st_id, &legacy_uuid);
-    return mrg_metric_get_and_acquire(main_mrg, &legacy_uuid, (Word_t) ctx);
-}
-
-// ----------------------------------------------------------------------------
-// metric handle
-
-void rrdeng_metric_release(STORAGE_METRIC_HANDLE *db_metric_handle) {
-    METRIC *metric = (METRIC *)db_metric_handle;
-    mrg_metric_release(main_mrg, metric);
-}
-
-STORAGE_METRIC_HANDLE *rrdeng_metric_dup(STORAGE_METRIC_HANDLE *db_metric_handle) {
-    METRIC *metric = (METRIC *)db_metric_handle;
-    return (STORAGE_METRIC_HANDLE *) mrg_metric_dup(main_mrg, metric);
-}
-
-STORAGE_METRIC_HANDLE *rrdeng_metric_get(STORAGE_INSTANCE *db_instance, uuid_t *uuid) {
-    struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
-    return (STORAGE_METRIC_HANDLE *) mrg_metric_get_and_acquire(main_mrg, uuid, (Word_t) ctx);
-}
-
-static METRIC *rrdeng_metric_create(STORAGE_INSTANCE *db_instance, uuid_t *uuid) {
-    internal_fatal(!db_instance, "DBENGINE: db_instance is NULL");
-
-    struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
-    MRG_ENTRY entry = {
-            .uuid = uuid,
-            .section = (Word_t)ctx,
-            .first_time_s = 0,
-            .last_time_s = 0,
-            .latest_update_every_s = 0,
-    };
-
-    METRIC *metric = mrg_metric_add_and_acquire(main_mrg, entry, NULL);
-    return metric;
-}
-
-STORAGE_METRIC_HANDLE *rrdeng_metric_get_or_create(RRDDIM *rd, STORAGE_INSTANCE *db_instance) {
-    struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
-    METRIC *metric;
-
-    metric = mrg_metric_get_and_acquire(main_mrg, &rd->metric_uuid, (Word_t) ctx);
-
-    if(unlikely(!metric)) {
-        if(unlikely(ctx->config.legacy)) {
-            // this is a single host database
-            // generate uuid from the chart and dimensions ids
-            // and overwrite the one supplied by rrddim
-            metric = rrdeng_metric_get_legacy(db_instance, rrddim_id(rd), rrdset_id(rd->rrdset));
-            if (metric)
-                uuid_copy(rd->metric_uuid, *mrg_metric_uuid(main_mrg, metric));
-        }
-
-        if(likely(!metric))
-            metric = rrdeng_metric_create(db_instance, &rd->metric_uuid);
-    }
-
-#ifdef NETDATA_INTERNAL_CHECKS
-    if(uuid_memcmp(&rd->metric_uuid, mrg_metric_uuid(main_mrg, metric)) != 0) {
-        char uuid1[UUID_STR_LEN + 1];
-        char uuid2[UUID_STR_LEN + 1];
-
-        uuid_unparse(rd->metric_uuid, uuid1);
-        uuid_unparse(*mrg_metric_uuid(main_mrg, metric), uuid2);
-        fatal("DBENGINE: uuids do not match, asked for metric '%s', but got metric '%s'", uuid1, uuid2);
-    }
-
-    if(mrg_metric_ctx(metric) != ctx)
-        fatal("DBENGINE: mixed up db instances, asked for metric from %p, got from %p",
-              ctx, mrg_metric_ctx(metric));
-#endif
-
-    return (STORAGE_METRIC_HANDLE *)metric;
-}
-
-
-// ----------------------------------------------------------------------------
-// collect ops
-
-static inline void check_and_fix_mrg_update_every(struct rrdeng_collect_handle *handle) {
-    if(unlikely((time_t)(handle->update_every_ut / USEC_PER_SEC) != mrg_metric_get_update_every_s(main_mrg, handle->metric))) {
-        internal_error(true, "DBENGINE: collection handle has update every %ld, but the metric registry has %ld. Fixing it.",
-              (time_t)(handle->update_every_ut / USEC_PER_SEC), mrg_metric_get_update_every_s(main_mrg, handle->metric));
-
-        if(unlikely(!handle->update_every_ut))
-            handle->update_every_ut = (usec_t)mrg_metric_get_update_every_s(main_mrg, handle->metric) * USEC_PER_SEC;
-        else
-            mrg_metric_set_update_every(main_mrg, handle->metric, (time_t)(handle->update_every_ut / USEC_PER_SEC));
-    }
-}
-
-static inline bool check_completed_page_consistency(struct rrdeng_collect_handle *handle __maybe_unused) {
-#ifdef NETDATA_INTERNAL_CHECKS
-    if (unlikely(!handle->pgc_page || !handle->page_entries_max || !handle->page_position || !handle->page_end_time_ut))
-        return false;
-
-    struct rrdengine_instance *ctx = mrg_metric_ctx(handle->metric);
-
-    uuid_t *uuid = mrg_metric_uuid(main_mrg, handle->metric);
-    time_t start_time_s = pgc_page_start_time_s(handle->pgc_page);
-    time_t end_time_s = pgc_page_end_time_s(handle->pgc_page);
-    time_t update_every_s = pgc_page_update_every_s(handle->pgc_page);
-    size_t page_length = handle->page_position * CTX_POINT_SIZE_BYTES(ctx);
-    size_t entries = handle->page_position;
-    time_t overwrite_zero_update_every_s = (time_t)(handle->update_every_ut / USEC_PER_SEC);
-
-    if(end_time_s > max_acceptable_collected_time())
-        handle->page_flags |= RRDENG_PAGE_COMPLETED_IN_FUTURE;
-
-    VALIDATED_PAGE_DESCRIPTOR vd = validate_page(
-            uuid,
-            start_time_s,
-            end_time_s,
-            update_every_s,
-            page_length,
-            ctx->config.page_type,
-            entries,
-            0, // do not check for future timestamps - we inherit the timestamps of the children
-            overwrite_zero_update_every_s,
-            false,
-            "collected",
-            handle->page_flags);
-
-    return vd.is_valid;
-#else
-    return true;
-#endif
-}
-
-/*
- * Gets a handle for storing metrics to the database.
- * The handle must be released with rrdeng_store_metric_final().
- */
-STORAGE_COLLECT_HANDLE *rrdeng_store_metric_init(STORAGE_METRIC_HANDLE *db_metric_handle, uint32_t update_every, STORAGE_METRICS_GROUP *smg) {
-    METRIC *metric = (METRIC *)db_metric_handle;
-    struct rrdengine_instance *ctx = mrg_metric_ctx(metric);
-
-    bool is_1st_metric_writer = true;
-    if(!mrg_metric_set_writer(main_mrg, metric)) {
-        is_1st_metric_writer = false;
-        char uuid[UUID_STR_LEN + 1];
-        uuid_unparse(*mrg_metric_uuid(main_mrg, metric), uuid);
-        netdata_log_error("DBENGINE: metric '%s' is already collected and should not be collected twice - expect gaps on the charts", uuid);
-    }
-
-    metric = mrg_metric_dup(main_mrg, metric);
-
-    struct rrdeng_collect_handle *handle;
-
-    handle = callocz(1, sizeof(struct rrdeng_collect_handle));
-    handle->common.backend = STORAGE_ENGINE_BACKEND_DBENGINE;
-    handle->metric = metric;
-    
-    handle->pgc_page = NULL;
-    handle->page_data = NULL;
-    handle->page_data_size = 0;
-    
-    handle->page_position = 0;
-    handle->page_entries_max = 0;
-    handle->update_every_ut = (usec_t)update_every * USEC_PER_SEC;
-    handle->options = is_1st_metric_writer ? RRDENG_1ST_METRIC_WRITER : 0;
-
-    __atomic_add_fetch(&ctx->atomic.collectors_running, 1, __ATOMIC_RELAXED);
-    if(!is_1st_metric_writer)
-        __atomic_add_fetch(&ctx->atomic.collectors_running_duplicate, 1, __ATOMIC_RELAXED);
-
-    mrg_metric_set_update_every(main_mrg, metric, update_every);
-
-    handle->alignment = (struct pg_alignment *)smg;
-    rrdeng_page_alignment_acquire(handle->alignment);
-
-    // this is important!
-    // if we don't set the page_end_time_ut during the first collection
-    // data collection may be able to go back in time and during the addition of new pages
-    // clean pages may be found matching ours!
-
-    time_t db_first_time_s, db_last_time_s, db_update_every_s;
-    mrg_metric_get_retention(main_mrg, metric, &db_first_time_s, &db_last_time_s, &db_update_every_s);
-    handle->page_end_time_ut = (usec_t)db_last_time_s * USEC_PER_SEC;
-
-    return (STORAGE_COLLECT_HANDLE *)handle;
-}
-
-void rrdeng_store_metric_flush_current_page(STORAGE_COLLECT_HANDLE *collection_handle) {
-    struct rrdeng_collect_handle *handle = (struct rrdeng_collect_handle *)collection_handle;
-
-    if (unlikely(!handle->pgc_page))
-        return;
-
-    if(pgd_is_empty(handle->page_data))
-        pgc_page_to_clean_evict_or_release(main_cache, handle->pgc_page);
-
-    else {
-        check_completed_page_consistency(handle);
-        mrg_metric_set_clean_latest_time_s(main_mrg, handle->metric, pgc_page_end_time_s(handle->pgc_page));
-        pgc_page_hot_to_dirty_and_release(main_cache, handle->pgc_page);
-    }
-
-    mrg_metric_set_hot_latest_time_s(main_mrg, handle->metric, 0);
-
-    handle->pgc_page = NULL;
-    handle->page_flags = 0;
-    handle->page_position = 0;
-    handle->page_entries_max = 0;
-    handle->page_data = NULL;
-    handle->page_data_size = 0;
-
-    // important!
-    // we should never zero page end time ut, because this will allow
-    // collection to go back in time
-    // handle->page_end_time_ut = 0;
-    // handle->page_start_time_ut;
-
-    check_and_fix_mrg_update_every(handle);
-
-    timing_step(TIMING_STEP_DBENGINE_FLUSH_PAGE);
-}
-
-static void rrdeng_store_metric_create_new_page(struct rrdeng_collect_handle *handle,
-                                                struct rrdengine_instance *ctx,
-                                                usec_t point_in_time_ut,
-                                                PGD *data,
-                                                size_t data_size) {
-    time_t point_in_time_s = (time_t)(point_in_time_ut / USEC_PER_SEC);
-    const time_t update_every_s = (time_t)(handle->update_every_ut / USEC_PER_SEC);
-
-    PGC_ENTRY page_entry = {
-            .section = (Word_t) ctx,
-            .metric_id = mrg_metric_id(main_mrg, handle->metric),
-            .start_time_s = point_in_time_s,
-            .end_time_s = point_in_time_s,
-            .size = data_size,
-            .data = data,
-            .update_every_s = (uint32_t) update_every_s,
-            .hot = true
-    };
-
-    size_t conflicts = 0;
-    bool added = true;
-    PGC_PAGE *pgc_page = pgc_page_add_and_acquire(main_cache, page_entry, &added);
-    while (unlikely(!added)) {
-        conflicts++;
-
-        char uuid[UUID_STR_LEN + 1];
-        uuid_unparse(*mrg_metric_uuid(main_mrg, handle->metric), uuid);
-
-#ifdef NETDATA_INTERNAL_CHECKS
-        internal_error(true,
-#else
-        nd_log_limit_static_global_var(erl, 1, 0);
-        nd_log_limit(&erl, NDLS_DAEMON, NDLP_WARNING,
-#endif
-                    "DBENGINE: metric '%s' new page from %ld to %ld, update every %ld, has a conflict in main cache "
-                    "with existing %s%s page from %ld to %ld, update every %ld - "
-                    "is it collected more than once?",
-                    uuid,
-                    page_entry.start_time_s, page_entry.end_time_s, (time_t)page_entry.update_every_s,
-                    pgc_is_page_hot(pgc_page) ? "hot" : "not-hot",
-                    pgc_page_data(pgc_page) == PGD_EMPTY ? " gap" : "",
-                    pgc_page_start_time_s(pgc_page), pgc_page_end_time_s(pgc_page), pgc_page_update_every_s(pgc_page)
-              );
-
-        pgc_page_release(main_cache, pgc_page);
-
-        point_in_time_ut -= handle->update_every_ut;
-        point_in_time_s = (time_t)(point_in_time_ut / USEC_PER_SEC);
-        page_entry.start_time_s = point_in_time_s;
-        page_entry.end_time_s = point_in_time_s;
-        pgc_page = pgc_page_add_and_acquire(main_cache, page_entry, &added);
-    }
-
-    handle->page_entries_max = data_size / CTX_POINT_SIZE_BYTES(ctx);
-    handle->page_start_time_ut = point_in_time_ut;
-    handle->page_end_time_ut = point_in_time_ut;
-    handle->page_position = 1; // zero is already in our data
-    handle->pgc_page = pgc_page;
-    handle->page_flags = conflicts? RRDENG_PAGE_CONFLICT : 0;
-
-    if(point_in_time_s > max_acceptable_collected_time())
-        handle->page_flags |= RRDENG_PAGE_CREATED_IN_FUTURE;
-
-    check_and_fix_mrg_update_every(handle);
-
-    timing_step(TIMING_STEP_DBENGINE_CREATE_NEW_PAGE);
-}
-
-static size_t aligned_allocation_entries(size_t max_slots, size_t target_slot, time_t now_s) {
-    size_t slots = target_slot;
-    size_t pos = (now_s % max_slots);
-
-    if(pos > slots)
-        slots += max_slots - pos;
-
-    else if(pos < slots)
-        slots -= pos;
-
-    else
-        slots = max_slots;
-
-    return slots;
-}
-
-static PGD *rrdeng_alloc_new_page_data(struct rrdeng_collect_handle *handle, size_t *data_size, usec_t point_in_time_ut) {
-    struct rrdengine_instance *ctx = mrg_metric_ctx(handle->metric);
-
-    PGD *d = NULL;
-    
-    size_t max_size = tier_page_size[ctx->config.tier];
-    size_t max_slots = max_size / CTX_POINT_SIZE_BYTES(ctx);
-
-    size_t slots = aligned_allocation_entries(
-            max_slots,
-            indexing_partition((Word_t) handle->alignment, max_slots),
-            (time_t) (point_in_time_ut / USEC_PER_SEC)
-    );
-
-    if(slots < max_slots / 3)
-        slots = max_slots / 3;
-
-    if(slots < 3)
-        slots = 3;
-
-    size_t size = slots * CTX_POINT_SIZE_BYTES(ctx);
-
-    // internal_error(true, "PAGE ALLOC %zu bytes (%zu max)", size, max_size);
-
-    internal_fatal(slots < 3 || slots > max_slots, "ooops! wrong distribution of metrics across time");
-    internal_fatal(size > tier_page_size[ctx->config.tier] || size < CTX_POINT_SIZE_BYTES(ctx) * 2, "ooops! wrong page size");
-
-    *data_size = size;
-
-    switch (ctx->config.page_type) {
-        case PAGE_METRICS:
-        case PAGE_TIER:
-            d = pgd_create(ctx->config.page_type, slots);
-            break;
-        case PAGE_GORILLA_METRICS:
-            // ignore slots, and use the fixed number of slots per gorilla buffer.
-            // gorilla will automatically add more buffers if needed.
-            d = pgd_create(ctx->config.page_type, GORILLA_BUFFER_SLOTS);
-            break;
-        default:
-            fatal("Unknown page type: %uc\n", ctx->config.page_type);
-    }
-
-    timing_step(TIMING_STEP_DBENGINE_PAGE_ALLOC);
-    return d;
-}
-
-static void rrdeng_store_metric_append_point(STORAGE_COLLECT_HANDLE *collection_handle,
-                                             const usec_t point_in_time_ut,
-                                             const NETDATA_DOUBLE n,
-                                             const NETDATA_DOUBLE min_value,
-                                             const NETDATA_DOUBLE max_value,
-                                             const uint16_t count,
-                                             const uint16_t anomaly_count,
-                                             const SN_FLAGS flags)
-{
-    struct rrdeng_collect_handle *handle = (struct rrdeng_collect_handle *)collection_handle;
-    struct rrdengine_instance *ctx = mrg_metric_ctx(handle->metric);
-
-    if(unlikely(!handle->page_data))
-        handle->page_data = rrdeng_alloc_new_page_data(handle, &handle->page_data_size, point_in_time_ut);
-
-    timing_step(TIMING_STEP_DBENGINE_CHECK_DATA);
-
-    pgd_append_point(handle->page_data,
-                     point_in_time_ut,
-                     n, min_value, max_value, count, anomaly_count, flags,
-                     handle->page_position);
-
-    timing_step(TIMING_STEP_DBENGINE_PACK);
-
-    if(unlikely(!handle->pgc_page)) {
-        rrdeng_store_metric_create_new_page(handle, ctx, point_in_time_ut, handle->page_data, handle->page_data_size);
-        // handle->position is set to 1 already
-    }
-    else {
-        // update an existing page
-        pgc_page_hot_set_end_time_s(main_cache, handle->pgc_page, (time_t) (point_in_time_ut / USEC_PER_SEC));
-        handle->page_end_time_ut = point_in_time_ut;
-
-        if(unlikely(++handle->page_position >= handle->page_entries_max)) {
-            internal_fatal(handle->page_position > handle->page_entries_max, "DBENGINE: exceeded page max number of points");
-            handle->page_flags |= RRDENG_PAGE_FULL;
-            rrdeng_store_metric_flush_current_page(collection_handle);
-        }
-    }
-
-    timing_step(TIMING_STEP_DBENGINE_PAGE_FIN);
-
-    // update the metric information
-    mrg_metric_set_hot_latest_time_s(main_mrg, handle->metric, (time_t) (point_in_time_ut / USEC_PER_SEC));
-
-    timing_step(TIMING_STEP_DBENGINE_MRG_UPDATE);
-}
-
-static void store_metric_next_error_log(struct rrdeng_collect_handle *handle __maybe_unused, usec_t point_in_time_ut __maybe_unused, const char *msg __maybe_unused) {
-#ifdef NETDATA_INTERNAL_CHECKS
-    time_t point_in_time_s = (time_t)(point_in_time_ut / USEC_PER_SEC);
-    char uuid[UUID_STR_LEN + 1];
-    uuid_unparse(*mrg_metric_uuid(main_mrg, handle->metric), uuid);
-
-    BUFFER *wb = NULL;
-    if(handle->pgc_page && handle->page_flags) {
-        wb = buffer_create(0, NULL);
-        collect_page_flags_to_buffer(wb, handle->page_flags);
-    }
-
-    nd_log_limit_static_global_var(erl, 1, 0);
-    nd_log_limit(&erl, NDLS_DAEMON, NDLP_NOTICE,
-                "DBENGINE: metric '%s' collected point at %ld, %s last collection at %ld, "
-                "update every %ld, %s page from %ld to %ld, position %u (of %u), flags: %s",
-                uuid,
-                point_in_time_s,
-                msg,
-                (time_t)(handle->page_end_time_ut / USEC_PER_SEC),
-                (time_t)(handle->update_every_ut / USEC_PER_SEC),
-                handle->pgc_page ? "current" : "*LAST*",
-                (time_t)(handle->page_start_time_ut / USEC_PER_SEC),
-                (time_t)(handle->page_end_time_ut / USEC_PER_SEC),
-                handle->page_position, handle->page_entries_max,
-                wb ? buffer_tostring(wb) : ""
-                );
-
-    buffer_free(wb);
-#else
-    ;
-#endif
-}
-
-void rrdeng_store_metric_next(STORAGE_COLLECT_HANDLE *collection_handle,
-                              const usec_t point_in_time_ut,
-                              const NETDATA_DOUBLE n,
-                              const NETDATA_DOUBLE min_value,
-                              const NETDATA_DOUBLE max_value,
-                              const uint16_t count,
-                              const uint16_t anomaly_count,
-                              const SN_FLAGS flags)
-{
-    timing_step(TIMING_STEP_RRDSET_STORE_METRIC);
-
-    struct rrdeng_collect_handle *handle = (struct rrdeng_collect_handle *)collection_handle;
-
-#ifdef NETDATA_INTERNAL_CHECKS
-    if(unlikely(point_in_time_ut > (usec_t)max_acceptable_collected_time() * USEC_PER_SEC))
-        handle->page_flags |= RRDENG_PAGE_FUTURE_POINT;
-#endif
-
-    usec_t delta_ut = point_in_time_ut - handle->page_end_time_ut;
-
-    if(likely(delta_ut == handle->update_every_ut)) {
-        // happy path
-        ;
-    }
-    else if(unlikely(point_in_time_ut > handle->page_end_time_ut)) {
-        if(handle->pgc_page) {
-            if (unlikely(delta_ut < handle->update_every_ut)) {
-                handle->page_flags |= RRDENG_PAGE_STEP_TOO_SMALL;
-                rrdeng_store_metric_flush_current_page(collection_handle);
-            }
-            else if (unlikely(delta_ut % handle->update_every_ut)) {
-                handle->page_flags |= RRDENG_PAGE_STEP_UNALIGNED;
-                rrdeng_store_metric_flush_current_page(collection_handle);
-            }
-            else {
-                size_t points_gap = delta_ut / handle->update_every_ut;
-                size_t page_remaining_points = handle->page_entries_max - handle->page_position;
-
-                if (points_gap >= page_remaining_points) {
-                    handle->page_flags |= RRDENG_PAGE_BIG_GAP;
-                    rrdeng_store_metric_flush_current_page(collection_handle);
-                }
-                else {
-                    // loop to fill the gap
-                    handle->page_flags |= RRDENG_PAGE_GAP;
-
-                    usec_t stop_ut = point_in_time_ut - handle->update_every_ut;
-                    for (usec_t this_ut = handle->page_end_time_ut + handle->update_every_ut;
-                         this_ut <= stop_ut;
-                         this_ut = handle->page_end_time_ut + handle->update_every_ut) {
-                        rrdeng_store_metric_append_point(
-                                collection_handle,
-                                this_ut,
-                                NAN, NAN, NAN,
-                                1, 0,
-                                SN_EMPTY_SLOT);
-                    }
-                }
-            }
-        }
-    }
-    else if(unlikely(point_in_time_ut < handle->page_end_time_ut)) {
-        handle->page_flags |= RRDENG_PAGE_PAST_COLLECTION;
-        store_metric_next_error_log(handle, point_in_time_ut, "is older than the");
-        return;
-    }
-
-    else /* if(unlikely(point_in_time_ut == handle->page_end_time_ut)) */ {
-        handle->page_flags |= RRDENG_PAGE_REPEATED_COLLECTION;
-        store_metric_next_error_log(handle, point_in_time_ut, "is at the same time as the");
-        return;
-    }
-
-    timing_step(TIMING_STEP_DBENGINE_FIRST_CHECK);
-
-    rrdeng_store_metric_append_point(collection_handle,
-                                     point_in_time_ut,
-                                     n, min_value, max_value,
-                                     count, anomaly_count,
-                                     flags);
-}
-
-/*
- * Releases the database reference from the handle for storing metrics.
- * Returns 1 if it's safe to delete the dimension.
- */
-int rrdeng_store_metric_finalize(STORAGE_COLLECT_HANDLE *collection_handle) {
-    struct rrdeng_collect_handle *handle = (struct rrdeng_collect_handle *)collection_handle;
-    struct rrdengine_instance *ctx = mrg_metric_ctx(handle->metric);
-
-    handle->page_flags |= RRDENG_PAGE_COLLECT_FINALIZE;
-    rrdeng_store_metric_flush_current_page(collection_handle);
-    rrdeng_page_alignment_release(handle->alignment);
-
-    __atomic_sub_fetch(&ctx->atomic.collectors_running, 1, __ATOMIC_RELAXED);
-    if(!(handle->options & RRDENG_1ST_METRIC_WRITER))
-        __atomic_sub_fetch(&ctx->atomic.collectors_running_duplicate, 1, __ATOMIC_RELAXED);
-
-    if((handle->options & RRDENG_1ST_METRIC_WRITER) && !mrg_metric_clear_writer(main_mrg, handle->metric))
-        internal_fatal(true, "DBENGINE: metric is already released");
-
-    time_t first_time_s, last_time_s, update_every_s;
-    mrg_metric_get_retention(main_mrg, handle->metric, &first_time_s, &last_time_s, &update_every_s);
-
-    mrg_metric_release(main_mrg, handle->metric);
-    freez(handle);
-
-    if(!first_time_s && !last_time_s)
-        return 1;
-
-    return 0;
-}
-
-void rrdeng_store_metric_change_collection_frequency(STORAGE_COLLECT_HANDLE *collection_handle, int update_every) {
-    struct rrdeng_collect_handle *handle = (struct rrdeng_collect_handle *)collection_handle;
-    check_and_fix_mrg_update_every(handle);
-
-    METRIC *metric = handle->metric;
-    usec_t update_every_ut = (usec_t)update_every * USEC_PER_SEC;
-
-    if(update_every_ut == handle->update_every_ut)
-        return;
-
-    handle->page_flags |= RRDENG_PAGE_UPDATE_EVERY_CHANGE;
-    rrdeng_store_metric_flush_current_page(collection_handle);
-    mrg_metric_set_update_every(main_mrg, metric, update_every);
-    handle->update_every_ut = update_every_ut;
-}
-
-// ----------------------------------------------------------------------------
-// query ops
-
-#ifdef NETDATA_INTERNAL_CHECKS
-SPINLOCK global_query_handle_spinlock = NETDATA_SPINLOCK_INITIALIZER;
-static struct rrdeng_query_handle *global_query_handle_ll = NULL;
-static void register_query_handle(struct rrdeng_query_handle *handle) {
-    handle->query_pid = gettid();
-    handle->started_time_s = now_realtime_sec();
-
-    spinlock_lock(&global_query_handle_spinlock);
-    DOUBLE_LINKED_LIST_APPEND_ITEM_UNSAFE(global_query_handle_ll, handle, prev, next);
-    spinlock_unlock(&global_query_handle_spinlock);
-}
-static void unregister_query_handle(struct rrdeng_query_handle *handle) {
-    spinlock_lock(&global_query_handle_spinlock);
-    DOUBLE_LINKED_LIST_REMOVE_ITEM_UNSAFE(global_query_handle_ll, handle, prev, next);
-    spinlock_unlock(&global_query_handle_spinlock);
-}
-#else
-static void register_query_handle(struct rrdeng_query_handle *handle __maybe_unused) {
-    ;
-}
-static void unregister_query_handle(struct rrdeng_query_handle *handle __maybe_unused) {
-    ;
-}
-#endif
-
-/*
- * Gets a handle for loading metrics from the database.
- * The handle must be released with rrdeng_load_metric_final().
- */
-void rrdeng_load_metric_init(STORAGE_METRIC_HANDLE *db_metric_handle,
-                             struct storage_engine_query_handle *rrddim_handle,
-                             time_t start_time_s,
-                             time_t end_time_s,
-                             STORAGE_PRIORITY priority)
-{
-    usec_t started_ut = now_monotonic_usec();
-
-    netdata_thread_disable_cancelability();
-
-    METRIC *metric = (METRIC *)db_metric_handle;
-    struct rrdengine_instance *ctx = mrg_metric_ctx(metric);
-    struct rrdeng_query_handle *handle;
-
-    handle = rrdeng_query_handle_get();
-    register_query_handle(handle);
-
-    if (unlikely(priority < STORAGE_PRIORITY_HIGH))
-        priority = STORAGE_PRIORITY_HIGH;
-    else if (unlikely(priority >= STORAGE_PRIORITY_INTERNAL_MAX_DONT_USE))
-        priority = STORAGE_PRIORITY_INTERNAL_MAX_DONT_USE - 1;
-
-    handle->ctx = ctx;
-    handle->metric = metric;
-    handle->priority = priority;
-
-    // IMPORTANT!
-    // It is crucial not to exceed the db boundaries, because dbengine
-    // now has gap caching, so when a gap is detected a negative page
-    // is inserted into the main cache, to avoid scanning the journals
-    // again for pages matching the gap.
-
-    time_t db_first_time_s, db_last_time_s, db_update_every_s;
-    mrg_metric_get_retention(main_mrg, metric, &db_first_time_s, &db_last_time_s, &db_update_every_s);
-
-    if(is_page_in_time_range(start_time_s, end_time_s, db_first_time_s, db_last_time_s) == PAGE_IS_IN_RANGE) {
-        handle->start_time_s = MAX(start_time_s, db_first_time_s);
-        handle->end_time_s = MIN(end_time_s, db_last_time_s);
-        handle->now_s = handle->start_time_s;
-
-        handle->dt_s = db_update_every_s;
-        if (!handle->dt_s) {
-            handle->dt_s = default_rrd_update_every;
-            mrg_metric_set_update_every_s_if_zero(main_mrg, metric, default_rrd_update_every);
-        }
-
-        rrddim_handle->handle = (STORAGE_QUERY_HANDLE *) handle;
-        rrddim_handle->start_time_s = handle->start_time_s;
-        rrddim_handle->end_time_s = handle->end_time_s;
-        rrddim_handle->priority = priority;
-        rrddim_handle->backend = STORAGE_ENGINE_BACKEND_DBENGINE;
-
-        pg_cache_preload(handle);
-
-        __atomic_add_fetch(&rrdeng_cache_efficiency_stats.query_time_init, now_monotonic_usec() - started_ut, __ATOMIC_RELAXED);
-    }
-    else {
-        handle->start_time_s = start_time_s;
-        handle->end_time_s = end_time_s;
-        handle->now_s = start_time_s;
-        handle->dt_s = db_update_every_s;
-
-        rrddim_handle->handle = (STORAGE_QUERY_HANDLE *) handle;
-        rrddim_handle->start_time_s = handle->start_time_s;
-        rrddim_handle->end_time_s = 0;
-        rrddim_handle->priority = priority;
-        rrddim_handle->backend = STORAGE_ENGINE_BACKEND_DBENGINE;
-    }
-}
-
-static bool rrdeng_load_page_next(struct storage_engine_query_handle *rrddim_handle, bool debug_this __maybe_unused) {
-    struct rrdeng_query_handle *handle = (struct rrdeng_query_handle *)rrddim_handle->handle;
-    struct rrdengine_instance *ctx = mrg_metric_ctx(handle->metric);
-
-    if (likely(handle->page)) {
-        // we have a page to release
-        pgc_page_release(main_cache, handle->page);
-        handle->page = NULL;
-        pgdc_reset(&handle->pgdc, NULL, UINT32_MAX);
-    }
-
-    if (unlikely(handle->now_s > rrddim_handle->end_time_s))
-        return false;
-
-    size_t entries = 0;
-    handle->page = pg_cache_lookup_next(ctx, handle->pdc, handle->now_s, handle->dt_s, &entries);
-
-    internal_fatal(handle->page && (pgc_page_data(handle->page) == PGD_EMPTY || !entries),
-                   "A page was returned, but it is empty - pg_cache_lookup_next() should be handling this case");
-
-    if (unlikely(!handle->page || pgc_page_data(handle->page) == PGD_EMPTY || !entries))
-        return false;
-
-    time_t page_start_time_s = pgc_page_start_time_s(handle->page);
-    time_t page_end_time_s = pgc_page_end_time_s(handle->page);
-    time_t page_update_every_s = pgc_page_update_every_s(handle->page);
-
-    unsigned position;
-    if(likely(handle->now_s >= page_start_time_s && handle->now_s <= page_end_time_s)) {
-
-        if(unlikely(entries == 1 || page_start_time_s == page_end_time_s || !page_update_every_s)) {
-            position = 0;
-            handle->now_s = page_start_time_s;
-        }
-        else {
-            position = (handle->now_s - page_start_time_s) * (entries - 1) / (page_end_time_s - page_start_time_s);
-            time_t point_end_time_s = page_start_time_s + position * page_update_every_s;
-            while(point_end_time_s < handle->now_s && position + 1 < entries) {
-                // https://github.com/netdata/netdata/issues/14411
-                // we really need a while() here, because the delta may be
-                // 2 points at higher tiers
-                position++;
-                point_end_time_s = page_start_time_s + position * page_update_every_s;
-            }
-            handle->now_s = point_end_time_s;
-        }
-
-        internal_fatal(position >= entries, "DBENGINE: wrong page position calculation");
-    }
-    else if(handle->now_s < page_start_time_s) {
-        handle->now_s = page_start_time_s;
-        position = 0;
-    }
-    else {
-        internal_fatal(true, "DBENGINE: this page is entirely in our past and should not be accepted for this query in the first place");
-        handle->now_s = page_end_time_s;
-        position = entries - 1;
-    }
-
-    handle->entries = entries;
-    handle->position = position;
-    handle->dt_s = page_update_every_s;
-
-    pgdc_reset(&handle->pgdc, pgc_page_data(handle->page), handle->position);
-
-    return true;
-}
-
-// Returns the metric and sets its timestamp into current_time
-// IT IS REQUIRED TO **ALWAYS** SET ALL RETURN VALUES (current_time, end_time, flags)
-// IT IS REQUIRED TO **ALWAYS** KEEP TRACK OF TIME, EVEN OUTSIDE THE DATABASE BOUNDARIES
-STORAGE_POINT rrdeng_load_metric_next(struct storage_engine_query_handle *rrddim_handle) {
-    struct rrdeng_query_handle *handle = (struct rrdeng_query_handle *)rrddim_handle->handle;
-    STORAGE_POINT sp;
-
-    if (unlikely(handle->now_s > rrddim_handle->end_time_s)) {
-        storage_point_empty(sp, handle->now_s - handle->dt_s, handle->now_s);
-        goto prepare_for_next_iteration;
-    }
-
-    if (unlikely(!handle->page || handle->position >= handle->entries)) {
-        // We need to get a new page
-
-        if (!rrdeng_load_page_next(rrddim_handle, false)) {
-            handle->now_s = rrddim_handle->end_time_s;
-            storage_point_empty(sp, handle->now_s - handle->dt_s, handle->now_s);
-            goto prepare_for_next_iteration;
-        }
-    }
-
-    sp.start_time_s = handle->now_s - handle->dt_s;
-    sp.end_time_s = handle->now_s;
-
-    pgdc_get_next_point(&handle->pgdc, handle->position, &sp);
-
-prepare_for_next_iteration:
-    internal_fatal(sp.end_time_s < rrddim_handle->start_time_s, "DBENGINE: this point is too old for this query");
-    internal_fatal(sp.end_time_s < handle->now_s, "DBENGINE: this point is too old for this point in time");
-
-    handle->now_s += handle->dt_s;
-    handle->position++;
-
-    return sp;
-}
-
-int rrdeng_load_metric_is_finished(struct storage_engine_query_handle *rrddim_handle) {
-    struct rrdeng_query_handle *handle = (struct rrdeng_query_handle *)rrddim_handle->handle;
-    return (handle->now_s > rrddim_handle->end_time_s);
-}
-
-/*
- * Releases the database reference from the handle for loading metrics.
- */
-void rrdeng_load_metric_finalize(struct storage_engine_query_handle *rrddim_handle)
-{
-    struct rrdeng_query_handle *handle = (struct rrdeng_query_handle *)rrddim_handle->handle;
-
-    if (handle->page) {
-        pgc_page_release(main_cache, handle->page);
-        pgdc_reset(&handle->pgdc, NULL, UINT32_MAX);
-    }
-
-    if(!pdc_release_and_destroy_if_unreferenced(handle->pdc, false, false))
-        __atomic_store_n(&handle->pdc->workers_should_stop, true, __ATOMIC_RELAXED);
-
-    unregister_query_handle(handle);
-    rrdeng_query_handle_release(handle);
-    rrddim_handle->handle = NULL;
-    netdata_thread_enable_cancelability();
-}
-
-time_t rrdeng_load_align_to_optimal_before(struct storage_engine_query_handle *rrddim_handle) {
-    struct rrdeng_query_handle *handle = (struct rrdeng_query_handle *)rrddim_handle->handle;
-
-    if(handle->pdc) {
-        rrdeng_prep_wait(handle->pdc);
-        if (handle->pdc->optimal_end_time_s > rrddim_handle->end_time_s)
-            rrddim_handle->end_time_s = handle->pdc->optimal_end_time_s;
-    }
-
-    return rrddim_handle->end_time_s;
-}
-
-time_t rrdeng_metric_latest_time(STORAGE_METRIC_HANDLE *db_metric_handle) {
-    METRIC *metric = (METRIC *)db_metric_handle;
-    time_t latest_time_s = 0;
-
-    if (metric)
-        latest_time_s = mrg_metric_get_latest_time_s(main_mrg, metric);
-
-    return latest_time_s;
-}
-
-time_t rrdeng_metric_oldest_time(STORAGE_METRIC_HANDLE *db_metric_handle) {
-    METRIC *metric = (METRIC *)db_metric_handle;
-
-    time_t oldest_time_s = 0;
-    if (metric)
-        oldest_time_s = mrg_metric_get_first_time_s(main_mrg, metric);
-
-    return oldest_time_s;
-}
-
-bool rrdeng_metric_retention_by_uuid(STORAGE_INSTANCE *db_instance, uuid_t *dim_uuid, time_t *first_entry_s, time_t *last_entry_s)
-{
-    struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
-    if (unlikely(!ctx)) {
-        netdata_log_error("DBENGINE: invalid STORAGE INSTANCE to %s()", __FUNCTION__);
-        return false;
-    }
-
-    METRIC *metric = mrg_metric_get_and_acquire(main_mrg, dim_uuid, (Word_t) ctx);
-    if (unlikely(!metric))
-        return false;
-
-    time_t update_every_s;
-    mrg_metric_get_retention(main_mrg, metric, first_entry_s, last_entry_s, &update_every_s);
-
-    mrg_metric_release(main_mrg, metric);
-
-    return true;
-}
-
-uint64_t rrdeng_disk_space_max(STORAGE_INSTANCE *db_instance) {
-    struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
-    return ctx->config.max_disk_space;
-}
-
-uint64_t rrdeng_disk_space_used(STORAGE_INSTANCE *db_instance) {
-    struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
-    return __atomic_load_n(&ctx->atomic.current_disk_space, __ATOMIC_RELAXED);
-}
-
-time_t rrdeng_global_first_time_s(STORAGE_INSTANCE *db_instance) {
-    struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
-
-    time_t t = __atomic_load_n(&ctx->atomic.first_time_s, __ATOMIC_RELAXED);
-    if(t == LONG_MAX || t < 0)
-        t = 0;
-
-    return t;
-}
-
-size_t rrdeng_currently_collected_metrics(STORAGE_INSTANCE *db_instance) {
-    struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
-    return __atomic_load_n(&ctx->atomic.collectors_running, __ATOMIC_RELAXED);
-}
-
-/*
- * Gathers Database Engine statistics.
- * Careful when modifying this function.
- * You must not change the indices of the statistics or user code will break.
- * You must not exceed RRDENG_NR_STATS or it will crash.
- */
-void rrdeng_get_37_statistics(struct rrdengine_instance *ctx, unsigned long long *array)
-{
-    if (ctx == NULL)
-        return;
-
-    array[0] = (uint64_t)__atomic_load_n(&ctx->atomic.collectors_running, __ATOMIC_RELAXED); // API producers
-    array[1] = (uint64_t)__atomic_load_n(&ctx->atomic.inflight_queries, __ATOMIC_RELAXED);   // API consumers
-    array[2] = 0;
-    array[3] = 0;
-    array[4] = 0;
-    array[5] = 0; // (uint64_t)ctx->stats.pg_cache_insertions;
-    array[6] = 0; // (uint64_t)ctx->stats.pg_cache_deletions;
-    array[7] = 0; // (uint64_t)ctx->stats.pg_cache_hits;
-    array[8] = 0; // (uint64_t)ctx->stats.pg_cache_misses;
-    array[9] = 0; // (uint64_t)ctx->stats.pg_cache_backfills;
-    array[10] = 0; // (uint64_t)ctx->stats.pg_cache_evictions;
-    array[11] = (uint64_t)__atomic_load_n(&ctx->stats.before_compress_bytes, __ATOMIC_RELAXED); // used
-    array[12] = (uint64_t)__atomic_load_n(&ctx->stats.after_compress_bytes, __ATOMIC_RELAXED); // used
-    array[13] = (uint64_t)__atomic_load_n(&ctx->stats.before_decompress_bytes, __ATOMIC_RELAXED);
-    array[14] = (uint64_t)__atomic_load_n(&ctx->stats.after_decompress_bytes, __ATOMIC_RELAXED);
-    array[15] = (uint64_t)__atomic_load_n(&ctx->stats.io_write_bytes, __ATOMIC_RELAXED); // used
-    array[16] = (uint64_t)__atomic_load_n(&ctx->stats.io_write_requests, __ATOMIC_RELAXED); // used
-    array[17] = (uint64_t)__atomic_load_n(&ctx->stats.io_read_bytes, __ATOMIC_RELAXED);
-    array[18] = (uint64_t)__atomic_load_n(&ctx->stats.io_read_requests, __ATOMIC_RELAXED); // used
-    array[19] = 0; // (uint64_t)__atomic_load_n(&ctx->stats.io_write_extent_bytes, __ATOMIC_RELAXED);
-    array[20] = 0; // (uint64_t)__atomic_load_n(&ctx->stats.io_write_extents, __ATOMIC_RELAXED);
-    array[21] = 0; // (uint64_t)__atomic_load_n(&ctx->stats.io_read_extent_bytes, __ATOMIC_RELAXED);
-    array[22] = 0; // (uint64_t)__atomic_load_n(&ctx->stats.io_read_extents, __ATOMIC_RELAXED);
-    array[23] = (uint64_t)__atomic_load_n(&ctx->stats.datafile_creations, __ATOMIC_RELAXED);
-    array[24] = (uint64_t)__atomic_load_n(&ctx->stats.datafile_deletions, __ATOMIC_RELAXED);
-    array[25] = (uint64_t)__atomic_load_n(&ctx->stats.journalfile_creations, __ATOMIC_RELAXED);
-    array[26] = (uint64_t)__atomic_load_n(&ctx->stats.journalfile_deletions, __ATOMIC_RELAXED);
-    array[27] = 0; // (uint64_t)__atomic_load_n(&ctx->stats.page_cache_descriptors, __ATOMIC_RELAXED);
-    array[28] = (uint64_t)__atomic_load_n(&ctx->stats.io_errors, __ATOMIC_RELAXED);
-    array[29] = (uint64_t)__atomic_load_n(&ctx->stats.fs_errors, __ATOMIC_RELAXED);
-    array[30] = (uint64_t)__atomic_load_n(&global_io_errors, __ATOMIC_RELAXED); // used
-    array[31] = (uint64_t)__atomic_load_n(&global_fs_errors, __ATOMIC_RELAXED); // used
-    array[32] = (uint64_t)__atomic_load_n(&rrdeng_reserved_file_descriptors, __ATOMIC_RELAXED); // used
-    array[33] = 0; // (uint64_t)__atomic_load_n(&ctx->stats.pg_cache_over_half_dirty_events, __ATOMIC_RELAXED);
-    array[34] = (uint64_t)__atomic_load_n(&global_pg_cache_over_half_dirty_events, __ATOMIC_RELAXED); // used
-    array[35] = 0; // (uint64_t)__atomic_load_n(&ctx->stats.flushing_pressure_page_deletions, __ATOMIC_RELAXED);
-    array[36] = (uint64_t)__atomic_load_n(&global_flushing_pressure_page_deletions, __ATOMIC_RELAXED); // used
-    array[37] = 0; //(uint64_t)pg_cache->active_descriptors;
-
-    fatal_assert(RRDENG_NR_STATS == 38);
-}
-
-static void rrdeng_populate_mrg(struct rrdengine_instance *ctx) {
-    uv_rwlock_rdlock(&ctx->datafiles.rwlock);
-    size_t datafiles = 0;
-    for(struct rrdengine_datafile *df = ctx->datafiles.first; df ;df = df->next)
-        datafiles++;
-    uv_rwlock_rdunlock(&ctx->datafiles.rwlock);
-
-    ssize_t cpus = (ssize_t)get_netdata_cpus() / (ssize_t)storage_tiers;
-    if(cpus > (ssize_t)datafiles)
-        cpus = (ssize_t)datafiles;
-
-    if(cpus > (ssize_t)libuv_worker_threads)
-        cpus = (ssize_t)libuv_worker_threads;
-
-    if(cpus >= (ssize_t)get_netdata_cpus() / 2)
-        cpus = (ssize_t)(get_netdata_cpus() / 2 - 1);
-
-    if(cpus < 1)
-        cpus = 1;
-
-    netdata_log_info("DBENGINE: populating retention to MRG from %zu journal files of tier %d, using %zd threads...", datafiles, ctx->config.tier, cpus);
-
-    if(datafiles > 2) {
-        struct rrdengine_datafile *datafile;
-
-        datafile = ctx->datafiles.first->prev;
-        if(!(datafile->journalfile->v2.flags & JOURNALFILE_FLAG_IS_AVAILABLE))
-            datafile = datafile->prev;
-
-        if(datafile->journalfile->v2.flags & JOURNALFILE_FLAG_IS_AVAILABLE) {
-            journalfile_v2_populate_retention_to_mrg(ctx, datafile->journalfile);
-            datafile->populate_mrg.populated = true;
-        }
-
-        datafile = ctx->datafiles.first;
-        if(datafile->journalfile->v2.flags & JOURNALFILE_FLAG_IS_AVAILABLE) {
-            journalfile_v2_populate_retention_to_mrg(ctx, datafile->journalfile);
-            datafile->populate_mrg.populated = true;
-        }
-    }
-
-    ctx->loading.populate_mrg.size = cpus;
-    ctx->loading.populate_mrg.array = callocz(ctx->loading.populate_mrg.size, sizeof(struct completion));
-
-    for (size_t i = 0; i < ctx->loading.populate_mrg.size; i++) {
-        completion_init(&ctx->loading.populate_mrg.array[i]);
-        rrdeng_enq_cmd(ctx, RRDENG_OPCODE_CTX_POPULATE_MRG, NULL, &ctx->loading.populate_mrg.array[i],
-                       STORAGE_PRIORITY_INTERNAL_DBENGINE, NULL, NULL);
-    }
-}
-
-void rrdeng_readiness_wait(struct rrdengine_instance *ctx) {
-    for (size_t i = 0; i < ctx->loading.populate_mrg.size; i++) {
-        completion_wait_for(&ctx->loading.populate_mrg.array[i]);
-        completion_destroy(&ctx->loading.populate_mrg.array[i]);
-    }
-
-    freez(ctx->loading.populate_mrg.array);
-    ctx->loading.populate_mrg.array = NULL;
-    ctx->loading.populate_mrg.size = 0;
-
-    netdata_log_info("DBENGINE: tier %d is ready for data collection and queries", ctx->config.tier);
-}
-
-bool rrdeng_is_legacy(STORAGE_INSTANCE *db_instance) {
-    struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
-    return ctx->config.legacy;
-}
-
-void rrdeng_exit_mode(struct rrdengine_instance *ctx) {
-    __atomic_store_n(&ctx->quiesce.exit_mode, true, __ATOMIC_RELAXED);
-}
-/*
- * Returns 0 on success, negative on error
- */
-int rrdeng_init(struct rrdengine_instance **ctxp, const char *dbfiles_path,
-                unsigned disk_space_mb, size_t tier) {
-    struct rrdengine_instance *ctx;
-    uint32_t max_open_files;
-
-    max_open_files = rlimit_nofile.rlim_cur / 4;
-
-    /* reserve RRDENG_FD_BUDGET_PER_INSTANCE file descriptors for this instance */
-    rrd_stat_atomic_add(&rrdeng_reserved_file_descriptors, RRDENG_FD_BUDGET_PER_INSTANCE);
-    if (rrdeng_reserved_file_descriptors > max_open_files) {
-        netdata_log_error(
-            "Exceeded the budget of available file descriptors (%u/%u), cannot create new dbengine instance.",
-            (unsigned)rrdeng_reserved_file_descriptors,
-            (unsigned)max_open_files);
-
-        rrd_stat_atomic_add(&global_fs_errors, 1);
-        rrd_stat_atomic_add(&rrdeng_reserved_file_descriptors, -RRDENG_FD_BUDGET_PER_INSTANCE);
-        return UV_EMFILE;
-    }
-
-    if(NULL == ctxp) {
-        ctx = multidb_ctx[tier];
-        memset(ctx, 0, sizeof(*ctx));
-        ctx->config.legacy = false;
-    }
-    else {
-        *ctxp = ctx = callocz(1, sizeof(*ctx));
-        ctx->config.legacy = true;
-    }
-
-    ctx->config.tier = (int)tier;
-    ctx->config.page_type = tier_page_type[tier];
-    ctx->config.global_compress_alg = RRD_LZ4;
-    if (disk_space_mb < RRDENG_MIN_DISK_SPACE_MB)
-        disk_space_mb = RRDENG_MIN_DISK_SPACE_MB;
-    ctx->config.max_disk_space = disk_space_mb * 1048576LLU;
-    strncpyz(ctx->config.dbfiles_path, dbfiles_path, sizeof(ctx->config.dbfiles_path) - 1);
-    ctx->config.dbfiles_path[sizeof(ctx->config.dbfiles_path) - 1] = '\0';
-
-    ctx->atomic.transaction_id = 1;
-    ctx->quiesce.enabled = false;
-
-    rw_spinlock_init(&ctx->njfv2idx.spinlock);
-    ctx->atomic.first_time_s = LONG_MAX;
-
-    if (rrdeng_dbengine_spawn(ctx) && !init_rrd_files(ctx)) {
-        // success - we run this ctx too
-        rrdeng_populate_mrg(ctx);
-        return 0;
-    }
-
-    if (ctx->config.legacy) {
-        freez(ctx);
-        if (ctxp)
-            *ctxp = NULL;
-    }
-
-    rrd_stat_atomic_add(&rrdeng_reserved_file_descriptors, -RRDENG_FD_BUDGET_PER_INSTANCE);
-    return UV_EIO;
-}
-
-size_t rrdeng_collectors_running(struct rrdengine_instance *ctx) {
-    return __atomic_load_n(&ctx->atomic.collectors_running, __ATOMIC_RELAXED);
-}
-
-/*
- * Returns 0 on success, 1 on error
- */
-int rrdeng_exit(struct rrdengine_instance *ctx) {
-    if (NULL == ctx)
-        return 1;
-
-    // FIXME - ktsaou - properly cleanup ctx
-    // 1. make sure all collectors are stopped
-    // 2. make new queries will not be accepted (this is quiesce that has already run)
-    // 3. flush this section of the main cache
-    // 4. then wait for completion
-
-    bool logged = false;
-    size_t count = 10;
-    while(__atomic_load_n(&ctx->atomic.collectors_running, __ATOMIC_RELAXED) && count && !unittest_running) {
-        if(!logged) {
-            netdata_log_info("DBENGINE: waiting for collectors to finish on tier %d...", (ctx->config.legacy) ? -1 : ctx->config.tier);
-            logged = true;
-        }
-        sleep_usec(100 * USEC_PER_MS);
-        count--;
-    }
-
-    netdata_log_info("DBENGINE: flushing main cache for tier %d", (ctx->config.legacy) ? -1 : ctx->config.tier);
-    pgc_flush_all_hot_and_dirty_pages(main_cache, (Word_t)ctx);
-
-    netdata_log_info("DBENGINE: shutting down tier %d", (ctx->config.legacy) ? -1 : ctx->config.tier);
-    struct completion completion = {};
-    completion_init(&completion);
-    rrdeng_enq_cmd(ctx, RRDENG_OPCODE_CTX_SHUTDOWN, NULL, &completion, STORAGE_PRIORITY_BEST_EFFORT, NULL, NULL);
-    completion_wait_for(&completion);
-    completion_destroy(&completion);
-
-    finalize_rrd_files(ctx);
-
-    if(ctx->config.legacy)
-        freez(ctx);
-
-    rrd_stat_atomic_add(&rrdeng_reserved_file_descriptors, -RRDENG_FD_BUDGET_PER_INSTANCE);
-    return 0;
-}
-
-void rrdeng_prepare_exit(struct rrdengine_instance *ctx) {
-    if (NULL == ctx)
-        return;
-
-    // FIXME - ktsaou - properly cleanup ctx
-    // 1. make sure all collectors are stopped
-
-    completion_init(&ctx->quiesce.completion);
-    rrdeng_enq_cmd(ctx, RRDENG_OPCODE_CTX_QUIESCE, NULL, NULL, STORAGE_PRIORITY_INTERNAL_DBENGINE, NULL, NULL);
-}
-
-static void populate_v2_statistics(struct rrdengine_datafile *datafile, RRDENG_SIZE_STATS *stats)
-{
-    struct journal_v2_header *j2_header = journalfile_v2_data_acquire(datafile->journalfile, NULL, 0, 0);
-    void *data_start = (void *)j2_header;
-
-    if(unlikely(!j2_header))
-        return;
-
-    stats->extents += j2_header->extent_count;
-
-    unsigned entries;
-    struct journal_extent_list *extent_list = (void *) (data_start + j2_header->extent_offset);
-    for (entries = 0; entries < j2_header->extent_count; entries++) {
-        stats->extents_compressed_bytes += extent_list->datafile_size;
-        stats->extents_pages += extent_list->pages;
-        extent_list++;
-    }
-
-    struct journal_metric_list *metric = (void *) (data_start + j2_header->metric_offset);
-    time_t journal_start_time_s = (time_t) (j2_header->start_time_ut / USEC_PER_SEC);
-
-    stats->metrics += j2_header->metric_count;
-    for (entries = 0; entries < j2_header->metric_count; entries++) {
-
-        struct journal_page_header *metric_list_header = (void *) (data_start + metric->page_offset);
-        stats->metrics_pages += metric_list_header->entries;
-        struct journal_page_list *descr =  (void *) (data_start + metric->page_offset + sizeof(struct journal_page_header));
-        for (uint32_t idx=0; idx < metric_list_header->entries; idx++) {
-
-            time_t update_every_s;
-
-            size_t points = descr->page_length / CTX_POINT_SIZE_BYTES(datafile->ctx);
-
-            time_t start_time_s = journal_start_time_s + descr->delta_start_s;
-            time_t end_time_s = journal_start_time_s + descr->delta_end_s;
-
-            if(likely(points > 1))
-                update_every_s = (time_t) ((end_time_s - start_time_s) / (points - 1));
-            else {
-                update_every_s = (time_t) (default_rrd_update_every * get_tier_grouping(datafile->ctx->config.tier));
-                stats->single_point_pages++;
-            }
-
-            time_t duration_s = (time_t)((end_time_s - start_time_s + update_every_s));
-
-            stats->pages_uncompressed_bytes += descr->page_length;
-            stats->pages_duration_secs += duration_s;
-            stats->points += points;
-
-            stats->page_types[descr->type].pages++;
-            stats->page_types[descr->type].pages_uncompressed_bytes += descr->page_length;
-            stats->page_types[descr->type].pages_duration_secs += duration_s;
-            stats->page_types[descr->type].points += points;
-
-            if(!stats->first_time_s || (start_time_s - update_every_s) < stats->first_time_s)
-                stats->first_time_s = (start_time_s - update_every_s);
-
-            if(!stats->last_time_s || end_time_s > stats->last_time_s)
-                stats->last_time_s = end_time_s;
-
-            descr++;
-        }
-        metric++;
-    }
-
-    journalfile_v2_data_release(datafile->journalfile);
-}
-
-RRDENG_SIZE_STATS rrdeng_size_statistics(struct rrdengine_instance *ctx) {
-    RRDENG_SIZE_STATS stats = { 0 };
-
-    uv_rwlock_rdlock(&ctx->datafiles.rwlock);
-    for(struct rrdengine_datafile *df = ctx->datafiles.first; df ;df = df->next) {
-        stats.datafiles++;
-        populate_v2_statistics(df, &stats);
-    }
-    uv_rwlock_rdunlock(&ctx->datafiles.rwlock);
-
-    stats.currently_collected_metrics = __atomic_load_n(&ctx->atomic.collectors_running, __ATOMIC_RELAXED);
-
-    internal_error(stats.metrics_pages != stats.extents_pages + stats.currently_collected_metrics,
-                   "DBENGINE: metrics pages is %zu, but extents pages is %zu and API consumers is %zu",
-                   stats.metrics_pages, stats.extents_pages, stats.currently_collected_metrics);
-
-    stats.disk_space = ctx_current_disk_space_get(ctx);
-    stats.max_disk_space = ctx->config.max_disk_space;
-
-    stats.database_retention_secs = (time_t)(stats.last_time_s - stats.first_time_s);
-
-    if(stats.extents_pages)
-        stats.average_page_size_bytes = (double)stats.pages_uncompressed_bytes / (double)stats.extents_pages;
-
-    if(stats.pages_uncompressed_bytes > 0)
-        stats.average_compression_savings = 100.0 - ((double)stats.extents_compressed_bytes * 100.0 / (double)stats.pages_uncompressed_bytes);
-
-    if(stats.points)
-        stats.average_point_duration_secs = (double)stats.pages_duration_secs / (double)stats.points;
-
-    if(stats.metrics) {
-        stats.average_metric_retention_secs = (double)stats.pages_duration_secs / (double)stats.metrics;
-
-        if(stats.database_retention_secs) {
-            double metric_coverage = stats.average_metric_retention_secs / (double)stats.database_retention_secs;
-            double db_retention_days = (double)stats.database_retention_secs / 86400.0;
-
-            stats.estimated_concurrently_collected_metrics = stats.metrics * metric_coverage;
-
-            stats.ephemeral_metrics_per_day_percent = ((double)stats.metrics * 100.0 / (double)stats.estimated_concurrently_collected_metrics - 100.0) / (double)db_retention_days;
-        }
-    }
-
-//    stats.sizeof_metric = 0;
-    stats.sizeof_datafile = struct_natural_alignment(sizeof(struct rrdengine_datafile)) + struct_natural_alignment(sizeof(struct rrdengine_journalfile));
-    stats.sizeof_page_in_cache = 0; // struct_natural_alignment(sizeof(struct page_cache_descr));
-    stats.sizeof_point_data = page_type_size[ctx->config.page_type];
-    stats.sizeof_page_data = tier_page_size[ctx->config.tier];
-    stats.pages_per_extent = rrdeng_pages_per_extent;
-
-//    stats.sizeof_metric_in_index = 40;
-//    stats.sizeof_page_in_index = 24;
-
-    stats.default_granularity_secs = (size_t)default_rrd_update_every * get_tier_grouping(ctx->config.tier);
-
-    return stats;
-}
-
-struct rrdeng_cache_efficiency_stats rrdeng_get_cache_efficiency_stats(void) {
-    // FIXME - make cache efficiency stats atomic
-    return rrdeng_cache_efficiency_stats;
-}